There have been proposed four systems for contactlessly (wirelessly) supplying electric power: an inductive coupling system, a magnetic field resonance system, an electric field coupling system, and a radio wave receiving system. In recent years, of these four systems, the magnetic field resonance system has come to draw attention which features a capability of sufficient electric power transmission and a long power transmission distance. As the magnetic field resonance system, there has been proposed a one-to-N power feeding system in which a power transmission device transmits power to a plurality of wireless power reception devices by making use of the feature of the long power transmission distance (see, for example, PTL 1).
In PTL 1, the power transmission device searches for wireless power reception devices in proximity within a few meters of the power transmission device, by transmitting a predetermined pulse signal in a standby mode in which the power transmission device does not feed power. When a wireless power reception device transmits a unique ID thereof to the power transmission device, the power transmission device determines whether or not the wireless power reception device is an object to which power is to be fed. If it is determined that the wireless power reception device is an object to which power is to be fed, the power transmission device transmits electric power to the wireless power reception device. At this time, the power transmission device can transmit a unique code to the wireless power reception device so as to receive information on the amount of charge, an operating state, and so forth, on a device-by-device basis.
Further, to develop the one-to-N power feeding system, standardization of the specifications of an N-to-N wireless power feeding system in which a plurality of power transmission devices transmit electric power to a plurality of wireless power reception devices is in progress. For example, there has been published NPTL 1 (see NPTL 1). According to NPTL 1, a specification is defined such that a group is formed by a plurality of power transmission devices, and one of the power transmission devices in the group is set as a master device for controlling the overall power transmission and communication in the group.
Further, PTL 2 mentioned below proposes a system in which a plurality of power transmission devices are combined, and operate as one consolidated system.